LCDs are commonly used in a variety of consumer electronics devices including televisions, computer monitors, laptop computers and mobile devices. A typical LCD module can include an LCD cell, light guide, illumination source, and electronics. The illumination source can be located along one or more edges of the light guide and LCD cell and can include light emitting diodes (LEDs), fluorescent lamps, incandescent light bulbs, or any other suitable light source. In addition to producing light, the illumination source can generate an amount of waste heat. This waste heat can create several thermal management issues. In particular, there are several ways in which the waste heat produced by the illumination source can affect the color of light emitted from the LCD module.
First, when the illumination source is an LED light bar, an increase in temperature can change the color of light directly emitted from the illumination source. LEDs can be particularly susceptible to heat and an increase in temperature can change the color, or wavelength, of light emitted from the LEDs. This can be particularly important with white light because a human eye can differentiate small color changes in white light. LCDs can produce white light either by using white LEDs or a combination of colored LEDs that combine to produce white light. As the temperature of the LEDs increases, the resulting white light can shift towards the blue side of the spectrum. Thus, if the LED light bar increases in temperature, the color of an image displayed on the LCD cell can shift. Moreover, if one portion of the LED light bar is hotter than another portion, a color shift can be visible when looking from one portion of the LCD cell to another.
Second, liquid crystals within the LCD cell can be affected by waste heat as well. Liquid crystals can control the color of an individual pixel by adjusting the amount of white light that is directed into several color filters. As the temperature of a liquid crystal increases, the amount of white light passed into the color filters can change, altering the color of the pixel. The illumination source can be mounted along one edge of the LCD cell. Therefore, the heat generated by the illumination source can cause a side of the LCD cell near the illumination source to be hotter than a side opposite from the illumination source. This can result in a color shift across the screen that can be visible to a user.
Therefore, what is desired is a way to efficiently remove waste heat from an illumination source while maintaining an approximately uniform temperature across a nearby LCD cell.